The objective of this Program Project is to bring together four research groups and to apply their complementary expertise to the problem of how undifferentiated cells develop into insulin-secreting beta-cells in organizing islets of Langerhans. Deriving data from zebrafish, chicks, mice, and humans, each project focuses on different but overlapping steps in the progression from embryonic stem cells to organized islets. Ultimately this information will be applied to the development of strategies for the production of new islets for patients with diabetes. Project 1 (Bell) will focus on the identification, characterization and purification of pancreatic stem/progenitor cells. Using progenitor-specific promoters developed by German, cells at discrete stages of differentiation will be fluorescently tagged in transgenic mice. These mouse models will be used to isolate and characterize presumptive pancreatic stem/progenitor cells. In addition, genes involved in islet development identified by German, Hebrok and Stainier will be screened for mutations in human populations. Project 2 (German) will focus on the progression of pancreatic progenitor cells to differentiated beta-cells utilizing the fluorescent transgenics derived by Cell, transcription factor knockout mice previously developed in this lab, and the microarray core. These studies will generate a picture of the gene expression changes that occur during beta-cell genesis, and provide candidate genes will be tested for their ability to affect the beta- cell fate decision in collaboration with Bell, Hebrok, and Stainer. Project 3 (Hebrok) will study endocrine cell migration and islet formation. Using mouse genetic models, he will test the role of migration guidance molecules and extracellular matrix modulators in islet morphogenesis and function. He will test the hypothesis that proper islet formation is critical for optimal islet function and homeostasis both in mice (with German) and humans (with Bell). Project 4 (Stainer) will examine the role of endoderm specification from zebrafish in activating the endodermal program in embryonic stem cells, the first step in the pathway to differentiated beta-cells. The zebrafish model will also be used in two collaborations with German: first to characterize the function of progenitor-specific promoters and second to test the role of candidate beta-cell determination genes.